1. Field of the Invention
The present invention is directed to a method for avoiding shorts in the manufacture of layered electrical components including two electrodes disposed over each other separated by an insulating or a semiconducting layer, and particularly to a method for manufacturing thin-film solar cells consisting of amorphous silicon layers.
2. Description of the Prior Art
Thin-film solar cells are known in the art which are produced by deposition on a substrate of the layer sequence of a transparent base electrode, an active amorphous silicon layer, and a cover electrode. The structure and operation of such thin-film solar cells of amorphous silicon are described, for example, in the book by Heywang entitled "Amorphe und polykristalline Halbleiter," in the series "Halbleiter-Elektronik", Volume 18, (1984), pages 58-64.
Considerable currents can arise in large area solar cells, for example, greater than 1.5 amperes given an efficiency of 10 percent, a standard illumination of AM1 (100 mW/cm.sup.2) and 10.times.10 cm.sup.2 area. Under such circumstances, losses which can no longer be ignored arise due to series resistance or transfer resistances. In thin-film solar cells, shorts having a considerable influence on the efficiency of the cells can arise between the electrodes if the active semiconductor layer does not densely cover the base electrode, that is, if voids are present in the amorphous silicon.
In order to reduce the series resistance of solar cells, so-called finger electrode structures (grids) are applied to the cells. Such a solar cell having, for example, a layer sequence of a substrate, a base electrode of molybdenum, an amorphous silicon (n-i-p) layer structure, a semi-transparent cover electrode of indium-doped tin oxide, and a grid electrode is disclosed in U.S. Pat. No. 4,417,092. Shorts between the base electrode and the highly conductive cover electrode are particularly critical in the region of the grid electrode structure, and may make the cells unusable.
In order to avoid these difficulties, attempts have previously been made to burn away the shorts by applying a voltage to the cover electrode and to the base electrode or, after detection of a void in the silicon with a sensor, to burn off the cover and/or base electrode at that location with a laser. The former method has the disadvantage that the void may not be so highly resistant that an adequately high current cannot flow and the cover electrode cannot be too thick. The latter method is complicated and extremely expensive.